1. The Field of the Invention
The present invention relates generally to medical devices and methods. More specifically, the present invention relates generally to introducer sheaths and, in particular, to an introducer sheath that is assembled from individual components such that the individual components are resiliently locked together when assembled. The introducer sheath in accordance with the present invention is generally for use during minimally invasive medical procedures.
2. The Relevant Technology
A wide variety of introducer sheaths have been developed for medical use. Introducer sheaths are often used to access a vessel or artery to allow a surgical procedure to be performed. For example, introducer sheaths are often used for medical procedures that utilize catheters, such as angioplasty or stenting procedures. In practice, the introducer sheath is typically inserted into the patient's vasculature using the modified Seldinger technique. Under the Seldinger technique, a needle is first inserted into the vessel. A guidewire is then inserted through the needle and into the vessel. Next, the needle is removed and a sheath/dilator combination is advanced over the guidewire. The dilator is used to expand the puncture in the vessel to a size suitable to receive an introducer sheath. After the distal end of the sheath is disposed within the vessel, the dilator and guidewire are removed, thereby allowing access to the vessel.
Conventionally, introducer sheaths are formed of three or more components that require assembly: an elongated tubular member, a hub portion, and a hemostasis valve disposed within the hub portion. In some designs an introducer sheath may also include a strain relief member which is disposed adjacent the distal end of the hub and about the proximal end of the elongated tubular portion. A suitable example of such an assembly is shown in U.S. Pat. No. 5,807,350, which discloses an introducer sheath having a construction similar to that described above, the entirety of which is hereby incorporated herein by reference.
Introducer sheaths, such as that described above, are generally constructed of multiple pieces which must be assembled to form the sheath. In most cases, the distal end of the hub portion is molded over the elongated tubular member. While molding may produce a stronger part, there is the possibility of damaging a portion of the other components of the device during the process. Any such damage results in the entire device having to be thrown away. As a result, there is a need for a way to attach the proximal end of the tubular member to the distal end of the hub portion which still meets all of the requirements of the introducer sheath, including but not limited to forming a fluid seal and having sufficient strength between the attachment of the hub portion and the tubular member to remain attached, but does not require throwing the entire device away if a portion of the sheath is damaged during manufacturing or assembly.
Prior introducer sheaths with such a substantially unitary design had difficulty accounting for or accommodating the variations that occur in the manufacturing process. When a defect occurred, even if it is only in a portion of the sheath, the unit must be discarded resulting in higher manufacturing costs and lower yields.
Similarly, the unitary design of introducer sheaths made it difficult to change materials during the manufacturing process or even changing the design of the sheath itself. Where an overmolded process is used to create the unitary introducer sheath, all the portions of the sheath are subjected to the heat from the molding process. As a result, the manufacturing processing itself may result in an uncontrolled change in geometry or a general decrease in quality control. Thus, there is a need for a new introducer sheath having lower manufacturing costs and higher quality control while still retaining the important requirements for an introducer sheath.
In another embodiment, the introducer sheath may be manufactured to be splitable during use. That is, the elongated tubular member may have a pre-scored line or another feature that allows it to split along a pre-determined path. In these instances, the choice of the material for the tubular shaft must be balanced between being splitable and being kink resistant and providing good performance. Therefore, there is a need for an improved introducer sheath having good kink resistance and good splitting properties.